The invention relates to a method for axially drawing prewound coils into grooves of stators or rotors of electric machines by means of a draw-in star which can be pushed forward through the bores of the respective stators or rotors, wherein during the draw-in process cover strips of an insulating material are pushed behind the draw-in star into the grooves in front of their opening slits. The invention furthermore relates to a device suitable for the execution of the said method.
The draw-in devices used customarily consist of circumferentially arranged parallel draw-in laminations for covering the sharp edges of the stator or rotor core at the opening slits of the grooves, of parallel cover strip laminations, which are arranged in a ring shape directly radially outside of the draw-in laminations, for guiding the cover strips, and a draw-in star, which is axially displaceable in the space enclosed by the laminations. After the coils to be drawn in have been suspended in the slits between the laminations, and a stator or rotor core has been placed on the free ends of the draw-in laminations, the draw-in star moves forward up to the core and through its bore, takes along the coils in the process and draws them into the grooves of the core. Reference is made to DE-PS 19 18 485 and U.S. Pat. No. 3,968,556 in connection with the mode of functioning of such a draw-in device.
The draw-in star customarily is in the shape of a mushroom head with radial protrusions, which extend through the opening slits of the grooves of the core and push the coil wires in the grooves away from the opening slits, so that the cover strips in a position directly in front of the opening slits can be axially pushed into the grooves. In its end position, in which it has been completely pushed forward through the bore of the stator or rotor, the draw-in star also pushes the portions of the coil extending past the end face of the core, the so-called winding heads, radially outward.
Up to now, at the end of the draw-in movement, the pushers, which are used for pushing the cover strips into the grooves, have been retracted simultaneously with the draw-in star, whose radial protrusions frictionally slide along the cover strips in the course of this movement. It is possible here that the draw-in star pulls individual cover strips partially out of the grooves again. Because of this, the respective stators or rotors become rejects.
The object of the invention is based on improving the quality of the production, and in accordance with the proposal of the invention, this object is attained in connection with the method in that, following the complete draw-in of the coils, the cover strips pushed into the grooves are supported against a retrograde movement during a defined first portion of the return movement of the draw-in star.
The invention has the advantage that, following the partial retraction of the draw-in star from the end position, in which it was pushed forward the farthest, the coils which had been radially pushed back toward the exterior can partially spring back toward the interior, in the course of which they push the cover strips next to the opening slits firmly against the groove wall. The cover strips, which are clamped into place in this way, thereafter maintain their predetermined position, even if in the further course of the return movement of the draw-in star the support of the cover strips is also pulled back.
The device proposed for executing the method of the invention has, in partial agreement with the device in accordance with U.S. Pat. No. 3,968,556, a holder for a stator or rotor of an electric machine, a draw-in star, which can be displaced through its bore for drawing coils into its grooves, as well as cover strip laminations and pushers for introducing cover strips made of an insulated material into the grooves of the stator or rotor in front of their opening slits in the course of the forward movement of the draw-in star, and it is distinguished over the known device in that the pushers remain in their pushed-forward position, at least during a defined first portion of the return movement of the draw-in star, so that they axially support the cover strips and prevent them from being pulled back by the draw-in star through friction.
Although with the device in accordance with U.S. Pat. No. 3,968,556 cover strips are also axially supported against being pulled back during the return movement of the draw-in star, this is a set of further cover strips, which is only to be pushed into the grooves of core of a following stator during the next draw-in movement, and which, during a first conveying step, have initially been pulled out of the cover strip magazine by additional rear pushers, but were not pushed into the stator core during the same step, and which now must be supported in the rearward direction by small contact faces attached to the cover strip laminations, so that they are not taken along in the course of the return movement by the front pushers sliding along them.